That yellow mat is just perfect!
I have had many girls with all kind of mental blocks on beam. All of them have over came the block at one point, and these are the strategies we have used, if the gymnast can do the skill on low beam but not on the high beam:
1) Stack mats under the beam, to the beam height. Then two panel mats on the sides of the beam. If you are terrified, you can even throw that yellow mat over all of it! Ta daa, now you can't even see the beam. It feels like floor. Do the skill, and then gradually move one mat at the time. The steps should be TINY! If you start to hesitate or balk, go back to the step where you were comfortable and stay there until you are bored again. This works for the kids who have very severe blocks or fears.
2) Watch yourself do the skill on video, if you were once able to do it. Then close your eyes, and try to do the skill in your mind. At first this can be difficult! If you are not able to see yourself do the skill in your mind, watch the video again. Make sure that you are in a peaceful place and relaxed. Then try to see the same skill in your mind, but change the gymnast. It's no longer you, it's someone from your team that has the skill. Then make her do it in your head like zillion times. When you can do this, try to imagine the same skill, same gymnast, with YOUR leotard on. Is it hard? Practice, practice, practice. When you can do this, change her hair color to YOUR hair color. Take tiny steps like this, until YOU are the gymnast who is able to perform the skill in your mind. If you struggle, try to change something from the mental picture. If you can make changes that make no sense, like change the beam to pink, or put cotton candy under the beam, this can trick your mind and you don't see yourself falling anymore. Sounds silly, but works!
The last step of this mental training is to change perspective in your mental picture. At first you tried to see yourself from outside, but now you want to take an active role and imagine yourself doing the skill. So you don't see yourself anymore, you see what you are supposed to see when performing the skill. This is the hardest step, but if you can get there, you are closer to doing the skill!
3) When you have done the mental training at home enough, try to bring it to practice. Go to a quiet corner of the gym, close your eyes and do the skill in your mind, like you practiced. Do this many times. Then go to the beam area, do the skill on the low beam, then close your eyes and do the skill again in your mind. Then, immediately without thinking anything, go to the high beam, give yourself 5 seconds to go for it and do the skill with the yellow mat. If you can't do the skill in 5 seconds, jump off the beam, and repeat the mental practice and do the skill on the low beam again. Then try again. You can ONLY stay on the high beam for 5 seconds and then you have to go for it, or jump off. It's very important to remember, that you are NOT a failure, if you are not able to do the skill on that given day. At least you tried. You might need more mental training at home.